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Unfit for flowers

By Barry Fox

Cut flowers wilt and die faster if bacterial colonies are allowed to build up in their water. In patent application WO 2004/15413, the Dutch research institute TNO details a way to tell when the water needs changing.

A sample of vase water is poured into a jug containing a plunge filter. This is pushed down, concentrating bacteria in the sample at the bottom. The interior base of the jug is coated with a polymer that fluoresces in the presence of oxygen. Any bacteria present consume oxygen and reduce the fluorescence, so light emitted by the dye is …